Cell sorting is necessary, or important, in many different circumstances, e.g., medical treatment, diagnostics, etc. Further, for example, an effective defense against bioterrorism demands fast, safe methods of sorting and identifying biohazardous materials. This includes infectious pathogens and pathogen-infected cells. At present, there does not appear to be a way of making existing conventional cell-sorters safe for use with pathogens and pathogen-infected cells. This is because conventional cell sorters eject droplets of cell-bearing fluids into the open air. Once the pathogens are aerosolized, containment becomes essentially impossible. Likewise, there are serious shortcomings in conventional “lab-on-a-chip” designs for cell sorting because these systems cannot operate at high enough throughput to isolate meaningful or useful quantities of sorted objects.
In addition to the safety issues, most conventional cell-sorters also utilize single sort decision cell separation technologies. In other words, conventional cell sorters are only capable of a single sort/no-sort decision. If further sort decision levels are required, the single decision level sorted cells need to be collected and reintroduced at the input of the cell sorting instrument for an additional sorting pass.
Furthermore, most conventional microfluidic cell-sorters are slow (e.g., several hundred cell per second). Even present-day, non-microfluidic, high-speed flow cytometry and droplet-based cell sorting are slow, if large (e.g., 108 cells or more) numbers of cells need to be isolated. Conventional fluidic switching approaches such as those commercially available in the FACS-SortTIVI (Becton-Dickinson, Inc.), while efficient for a limited number of applications, are capable of sorting only a few hundred cells/sec and are not useful for large-scale sorting or sorting of rare cell subpopulations.
Additionally, one needs to be able to obtain live, undamaged cells suitable for further growth, testing or transplantation. This is difficult to obtain in high-speed droplet sorting due to fundamental explosive decompression and g-force deceleration problems associated with this approach. The pressure change from the flow cell side of the exit orifice to the open air occurs very quickly. This leads to the problem of explosive decompression, and can result in a cell membrane rupture, or a least cell damage, leading to decreased viability for use of such cells.
Thus, there continues to be a need for safe, sterile, high-speed, multi-parameter sorting of biological objects, such as cells, for national defense and for basic and clinical science.